A heavy oil furnace was used to melt and prepare graphite cast iron, and the studies were carried out on the cast iron added with Fe-Si-Mg and it's heat treatment, mechanical properties at room and high temperatures, and the microstructure were examined. To facilitate the comparison, the same examinations were made on common cast iron, cast iron containing phosphorous and ordinary cast steel.
  The summary of those examinations are as follows :
  1) When the D. C. I. pig is used and it is melted by Tamman furnace and the additional amount of Mg in Fe-Si-Mg is made about 0.6 % of the molten metal in weight, graphite becomes spheroidal and the structure of matrix is almost ferritic.
  So that said metal is melted by a heavy oil furnace.
  2) The hardness tests at room temperature and 400°C, the oil quenched spheroidal graphite cast iron showed a maximum hardness and the hardnesses are lowered in the order from quenched, tempered as-cast and annealed in furnace sample. But, the differences in hardness at 600°C of these samples were very small.
  The hardness of ordinary cast iron was a little inferior than that of spheroidal cast iron of as-cast state, and it almost similar to the hardness of cast iron containing phosphorous.
  The hardness of ordinary cast steel is almost same with that of spheroidal cast iron of furnace annealed.
  3) Same tendency obtained in hardness test can be seen in the wear resistance test from room temperature up to 500°C.
  4) The shock value of spheroidal graphite cast iron annealed in the furnace shows maximum at the room temperature shock test, and it decreases by the order as follows; quenched and tempered specimen, as-forged, and oil quenched.
  5) The matrix of oil quenched spheroidal graphite cast iron specimen when it is observed by a microscope, is martensite and that of quenched and tempered specimen is troostic martensite.

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  This study was carried out with the intention to know the foundation of cupola operation with surveying the relation between construction and reaction of cupola and their influences on melting condition. In the reports 1∼3, experiments and considerations were performed about the effects of cupola factors on the flow of wind in furnace and its fundamental character in the state of non combustion. In this report, melting rate, the properties of melts, gases distribution and the changes of wind pressure in the furnace were surveyed in the state of practical operation by using the same cupola.
  The results are summarized as follows :−
  In case of smaller tuyère, air distribution becomes ununiform especially with tuyère ratio of 25∼16, the furnace atmosphere is oxidizing, the melt is liable to be oxidized. Si loss is increased, eutectic graphite is apt to be produced and remarkable strength can not be obtained. On the contrary in the case of larger tuyère, the air distribution is uniform but both melting ratio and tapping temperature are decreased. In such a case, however, the blast pressure becomes larger with the increase of the blast volume and so the properties of the melts are improved.
  According to the above facts, the author considers that extremely large tuyère ratio is undesirable and should be reduced below 10.

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  In the previous report, the author explained the formation of a permanent wall at the lining surface with compulsory cooling.
  In this paper, he reports the basic cupola practice using a small cupola to estimate the application of this cooling method. The results obtained were as follows:
  The basic practice can be operated by the application of water cooling method to melting zone of the cupola which has been lined with thin basic materials. This lining remains permanently during operation and a greater uniformity of furnace conditions would be obtained.
  As better carburizing condition can be obtained by using the low basic slags, the production of high grade castings will be possible by charging a much cheaper steel scrap with large proportion. The use of hot blast is very effective in the process.

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  No difference in the quality of molten iron can be observed when the low sulphur coke (LSC coke) of 60∼80mm size and the Tekken Briquette Coke of 75mmH×75mmφ are mixed by the ratio of 50 : 50 and are used as the split coke in the case of melting the cast iron by the hot blast cupola (inside dia. 550mmφ, blast temperature 300∼350°C). The percentages of scrap in the past several years in our foundry and which due to a pin-hole defect appeared on the inside surface of the cylinder casting after machining finish with a honing machine are as follows:
  Percentages of scrap in the duration of the melting was performed with the use of LSC coke alone: 4.9%.
  Percentages of scrap in the duration of the melting was performed with the mixing use of LSC coke and the Tekken Briquette Coke: 4.2%.
  No great difference was obtained in the percentages of scrap due to pin hole defect.
  The mixing percentages of the Tekken Briquette Coke into the LSC coke reached to 28.5% in 1956 and the savings of fuel cost was attained to ￥. 200,000.
  Even though the quality of molten iron was improved, the percentages of scrap could not be lessened for the last several years, but it was possible to lessen it down to 1∼2% by improving the molding sand or the casting conditions.
  The automatic controlling apparatus was used to control the blast volume, so that the blowing quantity was maintained constant in this experiment.

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  The basic experiments on segregation have been conducted in order to substantiate the theoretical mechanism of the shape of segregation curves.
  Succeeding to the previous report, almost similar experiment was conducted this time ; i. e., by controlling the solidification process of the samples completely and four kinds of samples solidified at the different travelling rates of solidification were prepared, and segregation in these samples were determined.
  Aluminium of 99.07% purity and aluminium-copper alloy of 5.8%Cu were used for the preparation of the samples and thus the segregation of copper in the cases of different compositions was determined.
  The gists of the results are as follows:
  (1) The ranges of inverse segregation both in the firstly solidified and finally solidified regions became narrow as the purity of aluminium became high, consequently the slopes of these segregation curves became steep.
  This is due to the decreasing of the range of mushy zone in accompanying with the purity of sample.
  (2) The shape of normal segregation shows the change as if the diffusion coefficient becomes greater when the copper content of sample becomes higher.
  However, this change seems to be resulted not by the change of diffusion coefficient but by the change of the range of mushy zone.

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